A modem that's NOT for the Internet..

[sad69]

Whenever I try searching about modems on Google, I seem to come up with all sorts of Broadband modems, etc..

Recently, we've setup a VPN between our remote offices, and we're coming up against a speed issue. I think it's our ADSL provider, although there's not much to choose from (and we're with the biggest and cheapest..).

But basically what I'm wondering is that what if we had a modem at each office, and these modems all 'phone' eachother up over the regular phone lines. So these are connected directly, not over the Internet.

With this sort of setup, these are my questions:

Are there modems available that are capable to handling more than one connection? Or will we need multiple modems, etc.. at our main office?
In this sort of setup, how do we connect this to a router? Are IP Addresses still applicable? How do we actually see all these computers? I remember the BBS days, so I know something like this is possible..
How fast a modem can we get? Where would we find something like this? Is 56k the limit? Or is there faster?
Finally, is there a way to incorporate the Internet ontop of all of this? Like get the Internet at main office, and since everyone's connect through this network of modems, can they now have access to the Internet as well?


I'm not very knowledgeable in this area at all (as you may be able to tell.. not even sure if my questions are practical..), but I'm just trying to explore a new option that has come to mind.

We're not a HUGE company with millions of dollars, so it's not feasible to get a T1 - T4 line installed; we've checked and it's too much money. We figure that the phone line is not a HUGE expense and we'd be willing to pay the cash up front for the modems.

I've also recently read about SDSL.. does anyone know about this? Pricing and availability? I know that availability will depend on where our offices are, but I just wanted to get an idea (especially if anyone has any experience with it).

Just wanted to know your thoughts on this..

Thanks,
Sadiq.

[Roy Sinclair]

The company I used to work for did similar networking starting back in the days when it took four wire leased lines to run 4800 baud modems. At the last I knew about them those leased line modems ran at 56k simultaneously on both directions and using two dial up lines provided automatic swapover to switch lines (19.2k baud) in the event of failure of the leased lines. That was many years ago (before 56k dialup modems) and I think the ADSL and SDSL modems may be the descendants of those older modems. IIRC, ADSL is a system where a larger percentage of the bandwidth is dedicated to traffic in one direction while SDSL modems provide equivalent bandwith in both directions.

Now we ran those modems in two kinds of networking configurations, the first was a simple point to point configuration we used from our main data center to our company offices while the second configuration was a multi-drop configuration which connected a number of customers to our data center via a single modem at the data center.

We originally ran an asyncronous protocol over those lines so despite the syncronous capability of the lines we used only half of the available bandwith (actually less since there was also timing delays between messages) but later added devices which repackaged our asyncronous traffic inside a syncronous protocol between the sites and improved the throughput tremendously. I'm assuming you're thinking of running IP traffic which is a syncronous protocol to start with so that's probably not as important. Another speed boost we got was by adding data compression, most traffic is uncompressed data which can be compressed quite a bit so you may want to research that as a possible speed improvement.

With an IP network you're definitely going to want to have routers between your locations so that only traffic that really needs to go to any remote location goes there and that traffic from those remote locations only comes to your site when needed.

While it sounds like you've talked to your local phone companies you should also talk to your cable company. They also have a high speed network and may offer you a competive alternative, I know that at least 20 of the multitude of T1 lines my former company once used were actually provided by our local cable company and that was years before they got into the Internet provider business.

Also note, that while you say T1 is too expensive you might be able to afford "Fractional T1" lines (which is where I believe those SDSL modems come into play).

I don't know how helpful any of that may be but hopefully there's a possible direction buried in there that'll be useful.

[sad69]

Wow, no that's great Roy! Thanks, I'll be getting in touch with my cable company after the weekend and will ask about Fractional T1 lines of both companies.

I've still been researching, and came up with:
http://www.lightspeed.ca/superadsl.html

This is a company in my area that I'm looking to get in touch with. I think the 32 static IPs is overkill, but 1.9Mbps is nearly twice the upstream speed we're getting right now, so that should be an improvement! But management is really froogle, and I'm not sure they'll be prepared to spend this kind of money either..

Have you heard of this technology in your area?

We have VPN Routers at all the remote offices and one here at main office. It's primarily a Windows 2000 network, and we've got 2 Windows 2000 servers acting as domain controllers. Outside users are logging directly into the domain as are users within our main office. The speed isn't too much of an issue, however we're noticing that we'd like to store offsite backups over the Internet via FTP, and it takes forever -- and these files are compressed to the max!!

I'm also going to inquire about pricing and availability from Sprint about SDSL.

If you care, I can keep you posted as to what we decide next week.

Thank again,
Sadiq.